Conventionally, for example, as described in Japanese Laid-open Paten Publication No. 11-138051 (page 3, FIG. 1), a liquid treating device for separating and removing sludge from the used liquid coolant discharged from a machine tool has been known. Referring to the liquid treating device, liquid containing the sludge discharged to a liquid tank from the machine tool is pumped up by a pump and supplied to a cyclone filter. The liquid is swirled by the cyclone filter, and the sludge is subjected to centrifugal separation. Clean liquid is supplied to the machine tool, and dirty liquid containing the sludge is returned to the liquid tank.
Also, for example, Japanese Laid-open Patent Publication No. 2003-275938 (page 3, FIG. 1) discloses a coolant cleaning device. Referring to the coolant cleaning device, liquid containing sludge discharged to a liquid tank through a magnetic separator from the machine tool is pumped up by a pump, and is supplied to a cyclone device. The liquid is swirled by the cyclone device, and the sludge is subjected to centrifugal separation from the liquid. Clean liquid is supplied to a clean tank, and dirty liquid containing the sludge is circulated in the liquid tank through a sludge precipitation tank and a magnetic separator.
Since the liquid treating device described in Japanese Laid-open Patent Publication No. 11-138051 returns the dirty liquid containing the sludge to the liquid tank, a problem exists in that the sludge is not discharged to the exterior of a liquid circulatory system.
The coolant cleaning device described in Japanese Published Unexamined Patent Application No. 2003-275938 can discharge the sludge to the exterior of the liquid circulatory system, and the dirty liquid containing the sludge discharged from the lower part of the cyclone device is dropped to the sludge precipitation tank, and is treated. The liquid overflowed from the sludge precipitation tank is dropped to the magnetic separator, and is processed. The liquid dropped from the magnetic separator is further collected in the liquid tank. The treated liquid is sequentially descended, and thereby, sludge discharge devices such as the sludge precipitation tank and the magnetic separator must be set on the liquid tank being subjected to restrictions.
The present invention has been accomplished in view of the foregoing and other problems. It is an object of the present invention to provide a liquid treating device without any restrictions for a sludge discharge device that is set on a liquid tank.